Assistant Professor of Neurology and Neuro-Ophthalmology at UPMC, George T. Park, DO, started the Eye & Ear Foundation’s May 15 webinar, “Optic Neuritis: Symptoms, Causes, and Treatments,” by describing the topic as relevant and common.
Optic neuritis refers to an inflammation of the optic nerve. No diagnosis or cause is associated with it. The optic nerve is the whole area from the back of the eye to an area called the chiasm. Dr. Park likened the optic nerve as a cable that plugs the eye into the brain. Any inflammation in this area is optic neuritis.
The area is sub-segmented into multiple different segments, which is important because the area gives healthcare providers an idea as to what might be going on and what to expect on an exam.
Optic Neuritis Causes
Since there are multiple different etiologies, the following main six things need to be ruled out. It is especially important to get an infection ruled out because it would be treated very differently.
- Immune attack – most often MS or other autoimmune disease
- Infection – viruses or bacteria- syphilis, Lyme disease, shingles
- Toxins & medications – certain drugs, alcohol, or medications
- Nutritional – deficiency of vitamin B12, thiamine, or folate
- Cancer-driven – a distant tumor provokes an immune attack on the nerve
- Vascular – lost blood supply – a stroke of the optic nerve (one of more common causes in US)
Signs and Symptoms
The following classic triad is what would make Dr. Park think that the issue is inflammation of the optic nerve:
- Central vision loss – a blurry or dark spot appears in the middle of your sight, often within hours
- Colors look washed out – reds especially appear faded or gray; the world looks less vibrant
- Pain w eye movement – a dull ache behind the eye that gets worse when you look around
Exam
- Snellen chart (vision)
- Ishihara Plates (color) – a different color number in the background of a contrasting color
- Pupil response (reflex) – the pupil is sort of a marker for health and functioning of the optic nerve. Normal pupils constrict quickly and become very small when bright light is shone into them. If there is an injury, the rate of constriction is slower. If one nerve is injured and another is healthy, there will be contradictory dilatation.
- Optic nerve (structure) – have ability to look behind the eye and visualize the nerve itself and see signs of inflammation
A normal, healthy optic nerve should be a perfect circle that is a healthy, pink color. Blood vessels can be seen as they come in and out of the nerve.
Dr. Park pointed out that one thing that is confusing and can confuse providers is in inflammatory MS-associated optic neuritis, the nerve may appear normal. This, however, does not mean that there is no nerve inflammation.
When someone has an optic neuritis episode, a common step is to get an MRI of the brain. This allows the provider to visualize the brain, optic neuritis, and intracranial structures on different planes. It is very important for the MRI to be done with contrast because this makes nerve inflammation visible.
Demyelination
When it comes to MS-associated optic neuritis or inflammation from autoimmune disease, what is going on in the eye? Dr. Park compared the nerves in the body to an electrical wire. Just like an electrical wire, metal wires are in the middle – axons in the body – and rubber coating is on the outside. In the human body, this coating is made of myelin. When this area is inflamed and being damaged, it is called demyelination – essentially stripping that rubber coating on the outside, or the myelin sheath. If there is enough damage, it can damage the axon and lead to permanent vision loss.
Treatment
The first line of treatment is high-dose intravenous steroids. This has been the standard since the landmark Optic Neuritis Treatment Trial.
In refractory or severe cases, treatment is plasmapheresis, in which a plasma exchange removes harmful antibodies when steroids alone are not enough. It is similar to dialysis. Deciding to go this route is not always easy to initiate because it is very labor intensive on the body and often requires a hospital stay. It has been very effective, however.
Clinical trials are on the horizon, such as studies like the pCori Trial, which will test whether early plasmapheresis improves outcomes in severe cases. “What we’re finding more and more is if you initiate it earlier with patients, perhaps that can improve the visual outcome,” Dr. Park said. Patients with severe vision loss will be enrolling soon in a clinical trial that will start plasmapheresis early.
Visual Prognosis
Will your vision come back? The good news is that most patients recover well and are often back to their normal vision. Recovery initially occurs within the first month. Many different studies have found that somewhere near the six-month mark, a large percentage of people reached near normal vision. At the 15-year mark, the number is closer to 70%.
“Visual acuity is not the only aspect of vision, but it is important to be seen and treated properly to make sure you are not in the 30% category with a poor visual outcome,” Dr. Park said.
What are the chances of going on to develop MS after one episode of optic neuritis? The average risk across all patients is 50%. If the brain MRI is clean (normal) at presentation, the risk is 25%. However, if the brain MRI shows lesions at presentation and is therefore abnormal, the risk is 72%. Optic neuritis is the first sign of MS in 1 in 5 people who go on to develop the disease.
This is why an MRI is so important, Dr. Park emphasized. It is important to be seen and evaluated properly if you have an optic neuritis episode.
Key Takeaways
- Optic neuritis is inflammation of the optic nerve. It can have many causes – most commonly autoimmune, but also infection, toxins, and others
- Watch for three classic symptoms: Sudden central vision loss, pain with eye movement, and loss of color vision
- See a specialist promptly. A thorough exam plus early brain MRI is essential to find the cause and guide treatment
- IV steroids are the gold-standard treatment. Plasmapheresis is added for severe cases that don’t respond to steroids
- Most patients recover well. Long-term vision is usually good – but follow up matters, since optic neuritis can be the first sign of MS